Industrial nitrocellulose is available in various grades of nitration, i.e., high 11.8-12.2% and medium 11.2-11.8% and low 10.8-11.2%.
For over 30 years the production of nitrocellulose has not experienced many significant changes. British Pat. 336,235 to Imperial Chemical Industries Limited (ICI) describes a method of cutting cellulose into pieces prior to the nitration process such that the nitrocellulose produced thereby has good bulk flow properties. U.S. Pat. No. 2,028,080 to Hercules Powder Co. describes the preparation of a fibrous, form of nitrocellulose. British Pat. 1,175,607 to Nitrochemie Gesellschaft discloses that compacted and pourable nitrocellulose can be produced by moistening alcohol wet nitrocellulose with a solvent/plasticizer mixture and kneading to increase bulk density from 120 g/l up to 365 g/l. U.S. Pat. No. 3,284,253 to Hercules Incorporated discloses the steps of heating nitrocellulose, treating with a solvent, distillation of solvent, separating excess water, displacing absorbed water and recovering nitrocellulose granules. U.S. Pat. No. 3,325,315 to Hercules Incorporated discloses the production of a spheroid form of nitrocellulose by the steps:
(a) forming a slurry with agitation of nitrocellulose fibers which are substantially free of water and also substantially free of fiber aggregates in a volatile organic liquid mixture of hydrocarbon diluent and nitrocellulose solvent in the absence of a water-soluble protective colloid;
(b) the organic liquid mixture being only a softening and swelling agent for the nitrocellulose fibers;
(c) subjecting the resulting slurry of nitrocellulose fibers to high shear agitation, whereby the fibers become softened and swollen and break down into tiny, smooth-surfaced, rounded particle;
(d) initiating hardening of the resulting shaped particles of softened and swollen nitrocellulose by diluting the slurry with hydrocarbon diluent while continuing high shear agitation; and
(e) removing substantially all the nitrocellulose solvent by distillation in the presence of excess hydrocarbon diluent to complete hardening and densification of the nitrocellulose particles.
U.S Pat. No. 3,324,572 to Hercules Incorporated discloses a densification process for nitrocellulose in which a water-soluble polymer is used such as a cellulose ether. British Pats. 1,000,876 and 1,051,561 to ICI describe plasticized nitrocellulose. U.S. Pat. No. 3,985,691 to Societe Nationale Des Poudres et Explosives discloses a particulate nitrocellulose composition comprising 10 to 30% by weight of a hydroxylic plasticizer containing at least one free hydroxyl group capable of reacting with an isocyanate group. U.S. Pat. No. 4,590,019 to Wolff Walsrode describes producing free-flowing nitrocellulose using a screw-extruder.
However, despite the considerable effort as evidenced by the patent literature, ease of handling and safety consideration for solid nitrocellulose had remained a long sought after property prior to the present invention.